U.S. Pat. No. 2,744,147 discloses an alumina catalyst which may be promoted with a metal (cobalt, nickel and chromium) and a process using the catalyst in a fluidized bed for fluorinating haloalkanes at a temperature between 180.degree. to 425.degree. C. Haloalkanes which are disclosed which are suitable for fluorination include carbon tetrachloride, chloroform, 1,1,1-trichloroethane, methylene chloride, 1,1-dichloroethane, 1,1,2-trichloroethane, uns. tetrachloroethane, methylene bromide, bromoform, carbon tetrabromide, acetylene tetrabromide, dichlorofluoromethane, dichlorodifluoromethane, dibromodichloromethane and bromochlorodifluoromethane.
U.S. Pat. No. 2,744,148 discloses an alumina catalyst which may be promoted with a metal (chromium, cobalt, nickel, copper and palladium) and a process for fluorinating haloalkanes to highly fluorinated products. A process is disclosed which activates the catalyst and converts at least part of the alumina to basic aluminum fluorides.
U.S. Pat. No. 4,129,603 discloses and claims a process for the manufacture of 1,1,1,2-tetrafluoroethane which comprises reacting, in the vapor phase at elevated temperature, a haloethane of formula CX.sub.3 CH.sub.2 Y wherein X is bromine, chlorine or fluorine and Y is chlorine with hydrogen fluoride in the presence of a catalyst which is chromium (III) oxide or which is at least in part basic chromium (III) fluoride, and wherein the 1,1,1,2-tetrafluoroethane product contains 1,1-difluoro-2-chloroethylene as an undesirable impurity which is removed by intimate contact with a metal permanganate in a liquid medium. The impurity is difficult to remove from the product stream and requires additional capital investment to separate; in addition, the impurity leads to catalyst deactivation.
U.S. Pat. No. 4,158,675 discloses and claims a process for the manufacture of 1,1,1,2-tetrafluoroethane which comprises reacting, in the vapor phase at elevated temperature, a haloethane of formula CX.sub.3 CH.sub.2 Y wherein X is bromine, chlorine or fluorine and Y is chlorine with hydrogen fluoride in the presence of a catalyst which is chromium (III) oxide or which is, at least in part, basic chromium (III) fluoride, and wherein the 1,1,1,2-tetrafluoroethane product containing 1,1-difluoro-2-chloroethylene as impurity is brought together with hydrogen fluoride into contact with said catalyst which is chromium (III) oxide or which is at least in part basic chromium (III) fluoride at a temperature in the range 100.degree. C. to 275.degree. C. to reduce the amount of the impurity.
JP 55/27138 discloses and claims a process for the manufacture of 1,1,1,2-tetrafluoroethane which comprises reacting 1,1,1-trifluorochloroethane and hydrogen fluoride at a molar ratio of 1:3-20 in the presence of inorganic chromium (III) compounds at 300.degree.-450.degree. C. The preferred molar ratio of 1,1,1-trifluorochloroethane to hydrogen fluoride is 1:5-20. The reaction temperature is 350.degree.-420.degree. C. The reaction pressure is atmospheric pressure to 10 kg/cm.sup.2 G, and the reaction time is 1-30 seconds. The selectivity to 1,1,1,2-tetrafluoroethane is high at high conversion. Chromium (III) compounds which are suitable for the reaction include the oxide, hydroxide, halide such as chloride, bromide, iodide and fluoride, and inorganic acid salts such as sulphate, nitrate, carbonate and phosphate. The chromium compound is pretreated at reaction conditions of temperature and pressure under an atmosphere of hydrogen fluoride for 1-5 hours to stabilize the activity.
In the above process a mole ratio of hydrogen fluoride/1,1,1-trifluorochloroethane of 1:1 produces 1-chloro-2,2-difluoroethylene as the major by-product. If the mole ratio is above 5:1 the selectivity to 1,1,1,2-tetrafluoroethane exceeds 95%. The conversion is negligible at 200.degree. C., but it reaches 20% above 350.degree. C. The conversion increases with temperature, but the selectivity decreases. Below 420.degree. C., the selectivity is above 95% at the mole ratio of 8:1, and it is above 90% below 450.degree. C.
GB 2,030,981 discloses the preparation of 1,1,1,2-tetrafluoroethane by reaction of 1,1,1-trifluorochloroethane with HF in the presence of an inorganic chromium (III) compound, in which 0.002-0.05 moles of oxygen per mole of 1,1,1-trifluorochloroethane is passed into the reaction system. The molar ratio of HF to 1,1,1-trifluorochloroethane is preferably 3-20:1; most preferably 5-12:1. Reaction temperature is 300.degree.-450.degree. C., most preferably 350.degree.-420.degree. C. and the reaction time is 1-30 seconds. The catalyst is chromium (III) oxyfluoride, oxide, hydroxide, halide, inorganic acid salt, or their hydrates. The high and selective conversion by the catalyst is maintained by addition of oxygen and loss of catalytic activity is retarded.
It is an object of this invention to prepare 1,1,1,2-tetrafluoroethane via fluorination of 1,1,1-trifluorochloroethane with HF in the presence of non-chromium catalysts. Additional objects are to provide a catalyst which can either maintain a high degree of activity and selectivity in the absence of oxygen (metals supported on aluminum fluoride) or can substantially prevent the formation of CF.sub.2 .dbd.CHCl (metals supported on carbon).